The broad aim of the proposed research is to find out more about how a person organizes and produces the movements involved in speech. We will build on our research in two areas: (1) computer modelling of the vocal tract in a speech synthesis system; (2) analytical descriptions of vocal tract shapes. On this basis we aim to construct a computer system which will accept an acoustic signal as an input, and will calculate the articulation that could have produced this signal. The success of the system will be evaluated by using as input the sound track from x-ray motion pictures of speech, and comparing the output of the system with the movements seen on the film.